Nef (Negative Regulatory Factor) is a protein expressed by primate lentiviruses. These include human immunodeficiency viruses (HIV-1 and HIV-2) and simian immunodeficiency virus (SIV). Nef is one of many pathogen-expressed proteins, known as virulence factors, which function to manipulate the host's cellular machinery and thus allow infection, survival or replication of the pathogen. Nef stands for Negative Factor. Alternative Names: F protein protein, ABIN protein, p27 protein, 3'ORF protein, HIV-1 nef protein, HIV 1 nef, Nef protein, C terminal core protein protein, VAN protein , HIV 1 nef protein, HIV-1 nef, Negative factor protein, ABIN1 protein, HIV-1 Nef protein, HIV1 nef